98 PRACTICAL ORGANIC CHEMISTRY
water to the residue an almost colourless oil separates out. Xlie
oil is removed by extraction with ether, dehydrated over calcium
chloride and distilled. When the ether has been driven off,
almost the whole of the residue (ethyl diethyl malonate) passes
over at 206—208°. Yield about 15 grams.
CH2.(CO.OC2H8)2 + NaOCoH5 = CHNa(CO.OC2H5).2 + C
Sodium ethyl malonate.
CHNa(CO.OQ>H5)2 + C2H5I = CH(C9HB) (CO.OC2H5)2
Ethyl malonic ester.
Properties.—Colourless liquid with an agreeable fruity smell ;
b. p. 207°, sp. gr. rooS at 18°.
To obtain the free acid, the ester is hydrolysed \vitb
caustic potash. To 15 grams caustic potash in strong
aqueous solution, 10 grams of the ester are slowly added
from a tap-funnel. At first an emulsion forms, which soon
solidifies to a white mass. This is heated on the water-
bath with frequent shaking for about three-quarters of a.n
hour, until* it becomes completely liquid. The hydrolysis is
then complete. The product is diluted with a little water,
neutralised with concentrated hydrochloric acid, and. the free
acid precipitated with a strong solution of calcium chloride
as the calcium salt. This is separated from the solution "by
filtration and concentrated hydrochloric acid added to the
calcium salt. From the acid solution the free ethyl maloriit:
acid is extracted by shaking with ether. After evaporating*
off the ether, the acid remains behind as a syrup, wnicli
solidifies when cold. This is redissolved in water, boil eel
with a little animal charcoal to free it from any adhering
colouring matter, filtered, and evaporated to syrupy con-
sistency on the water-bath. The colourless acid crystallises
on cooling. Yield about 5 grams.
C2H5CH(CO.OC2H5)2 + 2KOH = CoH5CH(COJC)0 + 2C2H5OII
C2H5CH(Cb2K)2 + 2HCl = QH5CH(COSH)8-+ 2KC1.
Ethyl malonic acid.
Properties.—Rhombic prisms; m. p. 111*5°, easily soluble in
water, alcohol, and ether.
Reaction.—i. Heat a gram or two of the acid in a test-
tube over a small flame and have at hand a second test-tutee
one-third full of lime water. The acid decomposes at i<3o s